(1) List<?> myList = new ArrayList<?>();

(2) ArrayList<?> myList = new ArrayList<?>();

Almost always the first one is preferred over the second one. The first has the advantage that the implementation of the List can change (to a LinkedList for example), without affecting the rest of the code. This will be a difficult task to do with an ArrayList, not only because you will need to change ArrayList to LinkedList everywhere, but also because you may have used ArrayList specific methods.

• https://stackoverflow.com/questions/2279030/type-list-vs-type-arraylist-in-java